Variable pump control of the sub-power, full power control, cross-power control

Power control

Separate power variable system in the two hydraulic pumps have a separate constant power regulator, each hydraulic pump flow only by the pump where the load pressure of the circuit, as shown in Figure 1a, Figure 1b for the dual pump characteristic curve. Split power system simply combines two constant power hydraulic pumps together, each hydraulic pump up to absorb 50% of the rated power of the diesel  iron punching machine engine. And only when each hydraulic pump in the pressure adjustment range P0 ≤ P ≤ Pmax work in order to use the full power. As the load pressure in each circuit is generally not equal, so the output of the hydraulic pump flow is not equal. The advantage of this system is that the flow rates of the two hydraulic pumps can be individually varied according to the load of the respective circuit, and the adaptability to the load is superior to the full power system. The main drawback is that: because each hydraulic pump can only absorb 50% of the power of the diesel engine, and when one of the hydraulic pump work under the starting pressure, the other a hydraulic pump can not absorb the diesel engine spare power, the diesel engine Power is not fully utilized, thus limiting the excavator’s ability to work, so this system in foreign large and medium-sized excavator was basically eliminated.

Figure 1 sub-power variable system

Figure 1 sub-power variable system

Full power control

Figure 2 full-power variable system

Figure 2 full-power variable system

In the full power variable system, the hydraulic pump power regulation in two forms. One is the two hydraulic pumps share a power regulator, such as Rexroth A8VO pump (the working principle shown in Figure 2a), the pressure of the two hydraulic pump pressure pump PA1, PA2 half of the sum of the role of the regulator On the realization of the two pump common variables; the other is the two hydraulic pump configuration of a regulator, such as the K3V Kawasaki pump (working principle shown in Figure 2b shown), the two regulators by hydraulic linkage, two hydraulic pumps Of the pressure oil into the pump regulator ring cavity and the other side of the hydraulic pump regulator small face cavity, the realization of hydraulic linkage, the small end face cavity area hydraulic hole punch and the ring cavity area equal to the pump pressure changes on the regulator Push the effect of equal, so that the two hydraulic pump swashplate swing angle equal to the output flow equal to the two specifications of the same and at the same time the action of the implementing agencies to maintain synchronization relationship. Determine the pressure of the hydraulic pump flow change is the sum of the two hydraulic pump working pressure P = P1 + P2, as long as the meet 2P0 ≤ P ≤ 2Pmax, the sum of the two hydraulic pump power always remains constant, not exceeding the diesel power. But the power of each hydraulic pump is proportional to its working pressure, in which a hydraulic pump may sometimes run under overload, the system features shown in Figure 3. The advantages are: first, under certain conditions to take full advantage of diesel engine power; second, two hydraulic pumps each can absorb all the power of the diesel engine to improve the operational capacity of the work device; third, simple structure. As a result of the above characteristics, full power variable pump hydraulic drilling machine manufacturers system in the excavator has been a large number of applications. The full-power variable system, its performance is not ideal, the single pump characteristic curve shown in Figure 4. The operating point of the hydraulic pump is always automatically adjusted along the abcde polyline, the actual maximum power, maximum flow and maximum pressure in three extreme working conditions. Excavator work is not always required maximum power, maximum flow and maximum pressure. If the diesel engine is in no-load operation, or the operating load is light and the working device is in a strong resistance to micro-movement, if the above characteristics will inevitably lead to energy waste, but can not control the operation of the hydraulic pump, the full power system can not Avoiding the presence of power loss. Current open center system is not a separate full-power control function, but with other control together, such as negative flow control, positive flow control, power change control. Most domestic excavator hydraulic system with full power control and negative flow control of the combination of the output power of the hydraulic pump to control, in order to reduce extreme conditions of power loss.

Figure 3 full-power variable system characteristics

Figure 3 full-power variable system characteristics

Figure 4 constant power variable single pump characteristics

Figure 4 constant power variable single pump characteristics

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Cross power control

As the sub-power variable system is only a simple combination of two hydraulic pumps, each pump up to absorb 50% of the power of the diesel engine, when a hydraulic pump work under the starting pressure, the other a hydraulic pump can not absorb the diesel free spare power. In view of this drawback, in the sub-power system, based on the emergence of cross-power control. Cross-power control in principle is a full-power regulation, and the full power control is different from the two hydraulic pump displacement can be different. Through the cross-linked configuration, the working pressure of the two hydraulic pumps interact with each other’s regulators hole punching machine. The output flow of each hydraulic pump depends not only on its own outlet pressure but also on the outlet pressure of the other hydraulic pump. If a hydraulic pump does not operate or operates at less than 50% of the total drive power, the second hydraulic pump automatically utilizes the remaining power, in extreme cases up to 100% of the total drive power. Crossover power control not only has the ability to adjust the output of the hydraulic pump according to the load of each hydraulic pump, but also make full use of the power of the diesel engine. However, the operating point of the cross-power control hydraulic pump is limited to the abcde fold line as shown in Fig. 4 and can not be changed in the plane condition under the fold line. At present, cross-power control is not a separate work, but with other control methods combine to limit the sum of the two-pump power, shown in Figure 5 is the cross-power control and pressure cut off the combination of control.

Drilling Machine for ring

When the system pressure is higher than the set pressure, the pressure cut-off valve will act, the system pressure enters the power. When the system pressure is lower than the set pressure, The variable regulator cylinder chamber, so that the displacement of the hydraulic pump smaller.

 

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